1. Field of the Invention
The present invention relates to a rotary cutter having a plurality of indexable cutter inserts releasably attached to the forward end of a tool body.
2. Prior Art
A rotary cutter, which comprises a plurality of indexable cutter inserts releasably attached to an outer periphery of a tool body, is extensively used as a face milling cutter, a side milling cutter and the like.
FIG. 5 depicts one conventional inserted tooth rotary cutter. In this cutter, a plurality of recesses are formed in a steel tool body 1 in circumferentially spaced relation to one another to provide chip pockets 2, and an insert-receiving recess 3 is formed in that face of each chip pocket 2 which faces in a direction of rotation of the tool body 1. An indexable cutter insert 4 is received in each of the insert-receiving recesses 3 and releasably secured thereto by means of a clamp wedge 5. A bore 6, for securing the tool body 1 to a suitable drive source, is formed through the axis of the tool body 1.
The conventional rotary cutter as described above; however, there are disadvantages in that since the tool body 1 is entirely formed of steel, it is heavy, so that its handling is difficult. In order to reduce the weight, the tool body 1 may be formed of aluminum. However, since aluminum is inferior in rigidity to steel, it has been impossible to form the tool body 1 entirely of aluminum, and the use of aluminum has been limited only to those portions which are not required to be strong. As a result, a substantial reduction in weight cannot be attained. In addition, inasmuch as steel and aluminum must be joined together, the manufacturing cost is inevitably increased, or, in some cases, the manufacture of the tool itself has been impossible.
Furthermore, in the illustrated conventional rotary cutter, the clamp wedge 5 is used when securing the insert 4 to the insert-receiving recess 3. Therefore, the portions adjacent to the insert-mounting recesses 3 are subjected to elastic deformation as indicated by the arrows A in FIG. 5, and hence the tool body 1 is subjected to such a distortion as to cause the diameter of the mounting bore 6 to shrink. As a result, it has become difficult to secure the tool body 1 to the drive source, and the cutting precision of the tool is lowered. The above problem regarding the distortion has conventionally been solved simply by enlarging the diameter of the mounting bore 6 by an amount of about 0.02 to 0.03 mm in advance, as illustrated in FIG. 7. However, this method is not completely satisfactory.
Moreover, when cutting a workpiece of steel or the like using the rotary cutter, cutting heat having a temperature of about 800.degree. C. is generated at the tip end of the cutting edge and this heat is transferred to the workpiece, the cutting debris, and the tool body 1. The tool body 1 is heated by the cutting heat thus transferred, and is subjected to thermal expansion. As a result, the dimensions in various portions of the tool change, and difficulty arises in the maintenance of cutting precision. Furthermore, when the cutting operation is continuously carried out for a prolonged period of time, the temperature of the tool body 1 becomes extremely high. As a result, it may be impossible to handle the tool by hand, and it may also become difficult to detach the tool from the drive source.